Shear induced collapse settlement of arid soils

This paper presents the results of studies of deformation, strength and collapsibility of loess soils. Samples were taken from Al Dalam in central Saudi Arabia, which resembles an arid region. These samples were subjected to various laboratory tests to determine their physical and engineering properties. Sets of oedometer and direct shear tests were carried out in which the initial dry density and the normal pressure at wetting and shearing were each varied in turn. Oedometer results indicate that collapse potential decreases with density and increases logarithmically with normal pressure. Shear induces further collapse potential which increase with density due to further destruction of soil fabric. A unique shear stress–shear strain relationship was obtained for specimens prepared at different initial fabrics. Dry and soaked failure envelopes were both non-linear in the low-pressure range. Wetting induced a reduction in the shear strength parameters. The results of the tests are reported, and the significance of each variable is assessed.     

Karst Hazard Assessment of Eastern Saudi Arabia

Karst phenomena exist in areas in the eastern part of Saudi Arabia, forming solution features such as sinkholes, collapsed dolines and solution caverns, as a result of the chemical leaching of the carbonate and evaporite formations by percolating water. The instability of these karst phenomena could produce land subsidence problems. This paper reviews the geology of documented karstic rock units in Saudi Arabia and proposes a simple engineering classification of the solution features characteristic of limestone. Two case histories in the Dhahran area, eastern Saudi Arabia, will be used as examples for the application of a modified engineering classification.     

Chemical stabilization of sabkha soils at high moisture contents

Vast expanses of arid, saline soils that occur along the Arabian Gulf seaboard and elsewhere possess a very low density and strength that necessitate improvement before any actual construction takesplace. For large-scale constructions, several field improvement techniques have recently been implemented with various degrees of success. In surficial, small-scale applications, chemical stabilization provides a potential technique to improve the inferior properties of these soils, known locally as sabkha. A literature search indicates that chemical stabilization of soils usingasphalt, lime and cement is usually conducted at lower moisture contents than the optimum. Such moisture contents are also much lower than the natural moisture content of sabkha, and if applied to sabkha in the field, this wouldrequire lowering the moisture content before any stabilization commenced; whichwould be neither feasible nor economical.

In this investigation, an eastern Saudi sabkha soil was chemically stabilized at its natural moisture level, which varies from 16% to 22%. In addition to the characterization of the soil and standard compaction tests, cement and lime sabkha mixtures were prepared at five additions and cured for up to 90 days in plastic wrap. Results indicate that cement-stabilized sabkha gained high strength with time and proved to have a potential use in construction.     

Compaction Induced Yield Stress

In order to realize more benefits and to have more effective output from the mechanical ground improvement projects, the field soils are subjected to over consolidation. This process induces a characteristic yield stress in the compacted soil mass similar to that exhibited by the soil masses subjected to natural processes of over consolidation during their geological life time. In view of the absence of any documented geotechnical engineering literature on such an important topic, this paper intends to throw some useful light on compaction induced yield stress in fine-grained soils. A detailed discussion of various factors contributing to the induced yield stress as a consequence of compaction is done. The results of the present experimental study indicates that the values of compaction induced yield stress increase from dry side of optimum to optimum compacted state. This stress may tend to achieve an equilibrium value or decrease beyond optimum compacted state depending upon the contribution from the coarser fraction composing the soil. It is also illustrated that the soils subjected to same compactive effort exhibit different values of yield stress as a consequence of clay mineralogical composition of the soils.     

Compressibility and swelling characteristics of Al-Khobar Palygorskite, eastern Saudi Arabia

Expansive soils are found in different locations in eastern Saudi Arabia. The area is arid with high temperatures, highly variable humidity and an excessive rate of evaporation compared to the low precipitation. This resulted in the formation of water sensitive soils. In the present investigation, line valve buildings for a sweet water feeder (1118 mm in diameter) were constructed on a highly expansive material consisting mainly of brown palygorskite and gray palygorskite with thin sheets of gypsum and limestone. Block samples from both palygorskites were brought to the laboratory and cores as well as remolded samples were obtained from the blocks. The two palygorskites were found to be highly plastic and have a very high swelling potential. The liquid limit (LL) and plastic limit (PL) values for the brown palygorskite are 261% and 140%, respectively. The gray palygorskite has a LL of a 285% and a PL of 123%. The oedometer free swell tests for the two palygorskites produced an expansion ranging between 31.8% and 42.5% for the remolded samples. However, the expansion for cores ranges between 8.3% and 19.3%. The constant volume pressure tests produced a stress in excess of 4240 kPa. The swell potential reached a steady state after four days while the swelling pressure reached a steady state in about 3 h. The paper addresses the geology of the area, the characterization of the geomaterial including mineralogical composition using X-ray diffraction and SEM techniques and the swelling characteristics of the material.     

Utilization of bituminous limestone ash from EL-LAJJUN area for engineering applications

The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization of the bituminous limestone in thermal power stations and /or retort processes. Limy ash has been prepared from the El-Lajjun bituminous limestone by direct combustion at 1,200, 950, and 525°C respectively. The laboratory tests have been selected with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the stabilization problematic soils from Jordan as brown soils and the clayey marl has revealed optimum results. The unconfined compressive strength of the parent brown soil and the clayey marl has been raised from 5 kg/cm² to 50 and 25 kg/cm², respectively. The CBR value has been raised from 4.5 to 150% for both problematic soil types. Various mortars and construction elements can be produced at normal room curing temperature without the use of ordinary Portland cement (OPC). Low quality sub-base and base course can be mixed with ash to produce cement treated base (CTB) and roller compacted concrete (RCC) without OPC. Durable pavements, embankments can be constructed with very long life and low cost. CTB and RCC utilizing ash can be used in dam construction instead of normal soil in earth fill dams. The high alkalinity of El-Lajjun ash is considered as a disadvantage to be utilized in normal concrete mixes for structural purposes. Ash only can be mixed with aggregates to produce lean concrete like for blinding purposes to be prepared for foundation activities.     

Effects of crude oil contamination on geotechnical properties of clayey and sandy soils

The southern coastal plain of Iran at the Persian Gulf encounters oil pollution due to the historical oil exploitation, related tanker navigations and accidents, and petrochemical industrial expansions in the recent years. Therefore, it is important to investigate the geochemical properties of oil-contaminated coastal soils and sediments for engineering and environmental purposes. Here, an extensive laboratory testing program was carried out to determine the effects of crude oil contamination on some of the geotechnical properties of clayey and sandy soils such as CL, SM and SP sampled from the coastal soils from this area. The testing included basic properties, Atterberg limits, compaction, direct shear, uniaxial compression and permeability tests on clean and contaminated soil samples at the same densities. The contaminated samples were prepared by mixing the soils with crude oil in the amount of 2%, 4%, 8%, 12%, and 16% by dry weight. The results indicated a decrease in strength, permeability, maximum dry density, optimum water content and Atterberg limits. Knowledge of these effects of oil contamination is important in coastal engineering and environmental remediation activities of the studied coastal plain.     

The Influence of Placement Conditions on the Swelling of Variable Clays

The swelling of clay when it is subjected to moisture increase is a complicated process found to be influenced by several factors. The clay??s level of response is highly dependent on its mineralogical composition and structure. Practicing geotechnical engineers use the placement state and general index properties to forecast the swelling behavior of the soils. The purpose of this study was to investigate the influence of placement conditions on various clays and to demonstrate that the swelling of a particular clay type should not be predicted using information and trends obtained for other clays with different origins. Clay from Saudi Arabia was used to investigate the influence of initial moisture content and initial dry density on swelling. The prediction models created by other researchers were compared to the measured values in this study. The swelling behavior of both initially dry and wet prepared bentonite was examined, and the rate at which swelling developed in the bentonite clay was studied. The role of clay content in the volume change of sand?Cbentonite mixtures was also investigated. It was concluded that the prediction of clay-swelling parameters should not be based on the properties of other clays with different origins and mineralogical compositions. The trends published in the literature should be taken as a general guide only, and the influence of moisture content and dry density on swelling should be verified for individual sites. Because clay content significantly influences the overall volume change, it should be carefully assessed in each case.     

Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils: a preliminary study

Soft soil stabilization has been practised for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental programme was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0?C10% and 0?C20%, respectively. In addition, combinations of lime?Cnatural pozzolana were added to soft soils at the same ranges. Test specimens were subjected to compaction tests, shear tests and unconfined compression tests. Specimens were cured for 1, 7, 28 and 90?days, after which they were tested for unconfined compression tests. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of lime and natural pozzolana. Since natural pozzolana is much cheaper than lime, the addition of natural pozzolana in lime?Csoil mix may particularly become attractive and can result in cost reduction of construction.     

疏浚淤泥固化土的压缩特性与结构屈服应力

河道疏浚拓宽以及港口新建扩建等不可避免地产生大量疏浚淤泥,如何处置大量废弃淤泥是工程界关注的一个重要研究课题。固化方法是目前处理疏浚淤泥的常用方法,其目的是将废弃淤泥处理成土工材料加以利用。处理后的淤泥固化土作为工程建设用土必须考虑其工程力学性能。为了研究疏浚淤泥固化土的压缩性状与结构屈服应力,进行了多组不同配比下淤泥固化土的压缩试验。通过室内一维压缩试验,研究了高含水率疏浚淤泥固化土的压缩性状,探讨了固化材料掺量、初始含水率、龄期等对固化土压缩变形特性和结构屈服应力的影响。压缩试验结果表明:与许多天然沉积结构性土及水泥土类似,疏浚淤泥固化土的压缩曲线均存在一个明显的结构屈服点。当上部荷载小于结构屈服应力之前,固化土的压缩性很小; 一旦上部荷载超过结构屈服应力之后,固化土的压缩性急剧增大。分析了淤泥固化土结构屈服应力的影响因素,并将由一维压缩试验得到的结构屈服应力(Py)与由无侧限抗压试验确定的抗压强度(qu)进行了比较,给出了两者之间的定量关系。疏浚淤泥固化土在屈服前后的压缩性状差异很大,这一研究成果对工程应用很有指导意义,当上部荷载较低时,可以充分利用其屈服前的低压缩性,但应确保上部荷载不能超出其结构屈服应力,以避免固化土在缺乏预兆的情况下发生突然破坏。     

Inherent heterogeneity of sediments in Dhahran, Saudi Arabia — a case study

The behavior and properties of sediments depend on their compositional characteristics and formation processes, as well as the environmental conditions during their geological history, i.e. post-formation processes. A vertical cut made in a hill in Dhahran, Saudi Arabia, reveals a vivid picture of the inherent heterogeneity of sediments that have been deposited at different geological ages. A review of the geology of the area, as well as laboratory tests, help to determine the possible causes of the variability of soil types and properties in the area. Laboratory tests include basic geotechnical tests, chemical tests, X-ray diffraction analysis, scanning electron microscopy, and thermal analysis. These tests are used to identify different rock types and soils from the face of the cut. The results of this study indicate that the material from this cut varies from clayey shale and limestone rock (Tertiary, lower Eocene) formed some 52 M.Y. to calcite-cemented sand and pure calcite rock formed in the Quaternary age.     

Assessing Stabilization Effectiveness of Combined Cement Kiln Dust and Quarry Fines on Pavement Subgrades Dominated by Black Cotton Soil

In developing technically viable and economically sustainable methods of improving soil properties to suit the requirements of engineering structures, designers/engineers are to take into consideration the availability and cost effectiveness of materials required for such improvement scheme. In line with this, the present study evaluates stabilization effectiveness of combined quarry fines (QF) and cement kiln dust (CKD) on subgrades dominated by black cotton soil (BC soil). The experimental programme included Atterberg limits, compaction and California bearing ratio (CBR) tests on soil mixtures prepared with a representative BC soil at constant dosage of 10 % QF and 0, 4, 8, 12 and 16 % CKD. Prior to testing, soil mixtures for CBR test prepared at optimum moistures and compacted with British standard light compaction effort were soaked for 96 h after curing for 28 days. Test data show that the addition of QF and CKD together reduced the plasticity index that resulted in rapid textural changes and eventual improvement in constructability, led to an increase in the optimum moisture content and a decrease in the maximum dry unit weight. Furthermore, the coupled effects of QF and CKD resulted in substantial increase in CBR strength of the composite specimens. Overall, mixtures created using the proposed QF and CKD ratios rendered the soil physically and mechanically stable producing results that are compatible with desired values for engineering performance typically required by various user agencies for pavement subgrades. This improvement scheme is not only cost effective, but it is capable of lessening the demand on non renewable resources thereby reducing the footprint of road construction projects in the environment.     

On the Investigations of Resilient Modulus of Residual Tropical Gravel Lateritic Soils from Senegal (West Africa)

Investigations on the mechanical behavior of compacted gravel lateritic soils have been the subject of several studies. Used as road materials, soils tests were mainly performed using standard tests. Static loads as unconfined compression test (UCT) remain the only engineering approach used. Alternative testing techniques can be chosen as supplementary tests for characterizing pavement materials. These researches were conducted so as to determine the response of these particular and problematic soils in its compacted form with road traffic loads. This paper presents the results of research conducted to investigate the effect of the soil compacity on the resilient modulus of lateritic soils. The influence of the percentage of cement added so as to stabilize each sample at the optimum modified proctor (OPM) State was also determined. Soil big specimens of around 180 mm diameter (with length to diameter aspect ratio of 2:1) were prepared according to the standard procedure described by AASHTO T 307 and then were subjected to repeated load triaxial tests. The models used, analyzed and developed in this paper are mainly the Andrei and the Uzan–Witczak universal model. Test results showed that the specimen compacity has no significant influence on the resilient modulus of the investigated gravel lateritic soils. Soil specimens with variation of the percentage of cement added exhibited the highest resilient modulus values while the specimens with variation of the compacity exhibited the lowest values. The resilient modulus variation seems to be independent of the level of stress.     

改良膨胀土筑堤技术研究

利用改良膨胀土作为高速公路路堤填筑材料是宁淮高速公路需要解决的主要问题。尽管室内试验论证可以用石灰改良膨胀土性质,但现场石灰改良土施工还要解决三大问题：石灰拌和均匀性和石灰含量的检测问题、现场压实方法和压实度控制问题、现场压实改良土的胀缩性和强度是否满足高等级公路路床和路基的要求问题。结合宁淮高速公路先导段施工,设计了试验段进行现场试验。试验结果表明,通过合理的施工工艺、有力的质量控制,改良膨胀土能够满足设计要求。改良土已经不具有膨胀土性质,胀缩性低,CBR强度高,是良好的路堤填筑材料。     

The shifting geopolitics of higher education: Inter/nationalizing elite universities in Kazakhstan,Saudi Arabia,and beyond

This article examines recent higher education projects in two resource-rich, developmental states: Kazakhstan and Saudi Arabia. These projects are indicative of broader trend across Asia to move beyond previous national universities, toward a state-initiated model of the globally competitive university, which is designed to become an regional hub for elite education. Drawing on a range of qualitative methods, I consider the geopolitical context in which these projects have been conditioned and materialized, with a focus on how they are legitimated by policy-makers in the two case countries. By reframing discussions about the globalization of higher education in terms of a geopolitics of higher education, I argue that the cases of Kazakhstan and Saudi Arabia are not exceptions set outside of the hegemonic liberal system, but that they are ‘mirrors’ of recent internationalization agendas undertaken by elite Western universities. Through considering localized discourses of promoting knowledge-based economies, I consider how elites simultaneously work with and reconfigure globally-hegemonic discourses, and specifically how these elite university projects are part of broader authoritarian political configurations in Kazakhstan and Saudi Arabia.     

Durability Characterization of Marls from the Region of Dalmatia,Croatia

Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid change in rock material from initial properties to soil-like properties. The sensitivity of a rock type against weatherability is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles. The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia. The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower than approximately 65%, a dry density lower than 2.4 Mg/m³, and values of water absorption higher than 5%.     

弱膨胀土工程特性及其路基处治对策

针对湖北襄-荆高速公路膨胀土,在室内开展了弱膨胀土的压实特性、胀缩性状、力学特性试验研究,发现压实膨胀土的工程性状受含水率与压实度的影响,胀缩特性是膨胀土的固有特性,其大小取决于起始湿度和密度;击实膨胀土的最佳含水量和最大干密度随击实功变化而变化,压实功愈大,土的最大干密度也愈大,而对应的最佳含水量愈小;膨胀土的CBR值随其含水率的变化规律类似于击实曲线,但CBR峰值含水率大于最佳含水率,为深入认识膨胀土的工程特性提供了帮助。因此,利用弱膨胀土填筑路堤时,不仅要考虑经过击实后的土的性质,而且还要考虑在填方建成、条件改变后土的性能;膨胀土路堤填筑除考虑压实度与CBR值要求外,尚需考虑胀缩总率的影响。最后,推荐了弱膨胀土路堤结构型式,并提出了弱膨胀土用于路堤填筑的控制标准。     

The Use of Municipal Solid Waste Incinerator Ash to Stabilize Dune Sands

Dune sands are problematic soils because they have low shear strength and are susceptible to collapse upon wetting. Dosages of municipal solid waste incinerator ash between 10 and 80?% were used to improve the engineering properties of dune sands. The soil-ash mixtures were allowed to cure for periods from 7 to 90?days. Laboratory tests such as compaction, unconfined compression, shear box and hydraulic conductivity tests were performed to measure the engineering characteristics of the stabilized material. The results showed that the maximum dry density remains approximately constant up to ash content of 30?% and then it decreases with the increase in ash content. The optimum water content increases with the increase in ash content. The unconfined compressive strength substantially increases with ash content up to 30?% and then decreases with the increase in ash content. The angle of friction follows similar trend to the unconfined compressive strength. However, the cohesion shows a steady increase with the ash content. The hydraulic conductivity of the stabilized material consistently decreases with the increase in the ash content. The effect of curing time on the hydraulic conductivity is minimal after 7?days of curing time. However, the unconfined compressive strength and the cohesion slightly increased with curing time up to 90?days.     

Using landforms of Saudi Arabia for scenic and recreational purposes (With special reference to the Riyadh area)

The landform of Saudi Arabia in general and the Riyadh area in particular have their own potentiality for scenic and recreational purposes. The higher lands or features which have well cemented material in some areas of Riyadh have been recommended for scenic use, while lower lands like wide natural lakes, sand dunes and others can be mostly used for recreational purposes. Such features and purposes found here may be extrapolated into other similar areas within Saudi Arabia and may be compared with other areas elsewhere in the world.     

Overview of some geological hazards in the Saudi Arabia

The Saudi Arabia has harsh environmental conditions which enhance some geomorphologic/geological processes more than in other areas. These processes create different geological hazards. The general physiography of the Saudi Arabia is characterized by the Red Sea coastal plains and the escarpment foothills called Tihama, followed by the Arabian Shield Mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. These types of geological hazards can be categorized into sand accumulations, earth subsidence and fissures, flash floods, problematic soils, slope stability problems, and karst problems. The current study gives an overview of all these hazards with examples, as well as develops a geo-hazard map for the Saudi Arabia. Our findings indicate that the desert environment needs much concern and care. National and international agencies have to join together with other people to keep the system balanced and to reduce the resulting geological hazards. Also, remedial measures should be proposed to avoid and reduce these natural hazards.